Boring bar



Oct. 27, i953 Y. POOLE I 2,556,742

BORING BAR Filed Dec. 19, 1950 /912 Il a A7 i; ii l Patented Oct. 27,1953 UNITED NSTATES PATENT oFFlcE 2,656,742 BORING BAR Loyd Y. Poole,Glendale, Calif. Application December 19, 1950, Serial No. 201,609

. 3 Claims.

lThis invention relates to boring bars and particularly to a formthereof so designed as to eliminate chattering at cutting loads at whichsuch chattering would ordinarily occur.

In machine tools employing boring bars for forming accurately machinedbores and especially in the case of long or deep bores, the tool bit isclamped to the distal end of 'a bar mounted on the tool slide of themachine and the bar is generally somewhat longer than the length ordepth of the bore. In making a cut with a boring bar the cutting speed,the depth of out and `the rate of feed must be so interrelated as toeffect the most elcient opera-tion consistent with the load capacity ofthe boring bar and especially in operations inwhich the distal end `ofthe bar is unsupported. When overloaded, the bar will spring away fromthe work surface and chatter with the resultant production of a` roughsurface and possible damage to or scrapping of the work. In

effect, the prior art boring bars may be. compared to immense tuningforks havingnatural periods of vibration. rlhe destruction of suchperiods of vibration would make possible the taking of faster or heaviercuts with the resultant increase in production and decrease of liabilityof damaged or scrapped work.

With these considerations in mind, it is an object of the presentinvention to provide albor- `ing bar for use with lathes or othermachine tools employed for iinishing internal circular surfaces which isso constructed as to eliminate chattering which would otherwise occurina conventional boring bar of the saine size and length under a giventool pointload.

Another object of the invention is `to provide a `boring bar containingaduantity offmercuryfor other heavy fluid enclosed within the distal l.or

tool carrying end thereof and effective to dampen vibrations incident tocutting operations.

Still another object ofthe invention is to provide a Vibration dampeningboring bar for finishing internal circular `surfaces rotating about ahorizontal axis.

A further object of theinvention is to provide,l

a vibration dampening boring `bar `for finishing `internal circularsurfaces rotating about a verti- A still further object'of theinventionis `to pro- Vide a vibration` dampening boring bar for use in verticallathes, boring mills and similar machine tools in which separatequantities of mercury or other heavy fluid are enclosed withinthe distalend of the boring bar.

Still another object of the invention is to pro4`` (Cl. 'T7-58) 2 vide avibration dampening boring bar which is `simple in construction,economicalto manufacture, and reliable in use. j

with `the foregoing objects in view, together with such other objectsand advantages as may subsequently appear, the invention `resides in theparts, and in the construction, combination, and arrangement of parts,disclosed by way of example, in the following speciiication of` certainlmodes of execution of the invention: reference being had to theaccompanying drawings which form a part of said specification and inwhich drawings: l

Fig. 1 is a side elevation of a boring bar embodying the invention: theboring bar being adapted for use in horizontal boring operations, Fig. 2is an elevation of thetool carrying end of the boring bar shown in Fig.l, a portion of the tool bit being broken away to disclose internalconstruction,

Fig. 3 is a top plan view of the tool carrying end'of the boring barshown in Fig.` 1,

Fig. 4 is asectional `View of the tool carrying end ofthe boring bar;the view being taken on the line 4--lll of Fig. 3, l

Fig. 5 is an end elevation of the tool Vcarrying end of a boring barembodying the invention and 'adapted for vertical boring operations,

"for vertical boring operations.

' Referring vnrst to Figs. 1 toN 4, inclusive, there 1s shown a boringbar Al having a diametrical slot 2 inV one end thereof in which a toolbit T is clamped by a set screw S. The illustrated tool blt ls provldedwith a single cutting point, but a double ended tool bit may be equallywell 1employed and the mode of mounting the tool` bit may be as shown orany of the other conventional and well known modes of securing a toolbit to a boring bar may be employed.` l

`.The boring bar I is provided with an axially disposed bore 3 extendingfrom the rear face of the tool bit slot 2 for a portion of the lengthofthe bar and this bore is partially filled with a `quantity ofmercuryor other heavy fluid 4 and closedlby a taper threaded screwv 5which engages threads at the outer endofthe bore 3. Itjhasbeen foundthat the presencoo` .the mercury `in the distal end ofthe bar dampensTing -the lnext chamber. Y 'the' bore is thusiilledafter `which4thelendrof "form of the invention. 4of the `bore and the number ofcompartments "into which 'it is.divided are matters of choice, .but Vtheapproximate proportions shown .in =the form of the invention may also beemployed for forming vertical bores, the fluid will be contained in asingle body at the lower end r-ofthe bar and will not be as effective todampen the tendency of the bar to vibrate as caribe achieved if thefluid is extended along v.a,portion.ofithe length of the bar. Theeniciencyfthebar will be increased, but a greater increase-in capacityand eiiiciency V:can be achieved by the forms of-- the inventionmowtoghe: described.

` ,To pro-vide. a convenient construction in-which the fluid is extendedalong `a `.portion of the --.length offa vertically .disposedboringYbar, the 'bal' 6 SPI'OVded "Wh211 aXa11YdSPOSedEbGTSi 25 ithe :barsadapted -for avertical boring may be o .-1 extending from `the ltoolfbitLend, which lbore is somewhat larger Iin :diameter .than theslot 1.8 inwhicha toolfbitf" is secu-redby.a..set.screw t-S'. ,aseries of vispacedannular chambers Q vlby a 1 seriesf of partition ,forming elementscomprising aiprimary elementdllrand oneor more second- The .interior `ofthe bore 5'! .is divided into ary elements Il. The primary element,includes a disc-likecenter portion .-I2 `adapted to'make a Vtight.ipresswfit with .the sborey-l .Vand..a.-pairgof .coaxially Hdisposed4.shan-k elements -I3 Land Id `projiting from `the yopposite fsides V,ofthe vdisc,V

While, each secondaryfpartition-iforming yelement comprises a partition.forming ."c'iisclike head portion I5 with a coaxially dispose'dshanklii proj ecting. from one side only.

VIn assembly, the-boring bar is.placed -vv'it-hthe .bore end uppermost.and La .quantity of mercury .or iotherheavy .fluidrsuiiicient to,partially Lfill the innermost cavity orrchamber i9 .isipoured .intothebore.l Theprimari/partition forming element Y, L is fthen pressed.ntosplace withv .the

shank portion i t3 positionedragainst @the bottom vof the bore.Nextanotherquantity of viluid is poured into the bore suflicienttoiillthe next `-chamber tothe desired extent iandla secondary .element.ll is pressed .into the .bore .with -the yhead portion I5 thereofengaging theendof ythe shank- M of. theprimary elementand Athusform-This `is .repeated .until the bore 'l .is closedbya screwrplug .l1tvvhich converted into a series of chambers each containing a quantityVof uid whichacttd dampen the tendencyvof the bar andtoolrtoivibratefand thereby to increase the cutting capacitythereof inthe same manner as in .the rstadescribed The .size :and .length ,axialbore i9 extending v4from the .-toollholding ,'s'lot 20 `which is.adapted tol-,holdV atoolbit .'I"

clamped therein by a set screw S. The annular, uid holding chambers 2lare formed by a series of balls 22 pressed into the bore one at a timewith alternate quantities of mercury each of which is sufdcient topartially ll the compartment formed between adjacent balls or betweenthe ball at either end and the bottom of the bore or the screw plug 23which both closes the end of the bore and bears against the row ,ofballsr inserted int-the bore.`

"The action of the boring Lbar *'thus' dampened Vis the same aspreviously described but to a V*slightly lesser extent. It has theadvantage of :being easier to manufacture since the compartment formingballs are ordinary bearing balls and Eina'ypurchased for that purposeand the sep- ,araternanufacture of separate partition forming means thusdispensed with.

the iirst described form of the invention, other conventional modes ofmounting the tool i bits may be `employed -i in the evertical 'type i ofbars A'instead of the f specific form shown -and @the tool bits-maybeeither sing-leorfdouble-ended, as desired. Further, it will be-apparentthat equally well V-employed 'for f horizontal boringoperations although more expensive .to malce for this purpose alone.Thus, 4'each illustrated, form of the Ainvention has Vits rovv-nsspecialffadvantages -but Valliforms are useful 'for ieitherehorizon-talor vertical boring.

While'the foregoing specication discloses-certain -forms Vof theinvention, it'isnot intended 'I that the invention shall f be limitedtowthe .exact aformsY so disclosedf andfit -will be. understoodithat theinvention embraces--allfsuch -modi-cations in the .parts and in t theconstruction, combina- Etion and 'arrangement i of parts as shall t,comeAvt-within the' purview* of the i appended claims.

lclaim: r1. A'boring` barfonuse with boringmillsyver- `tical lathesandjsimilar machineatoolsponeend "tof said bar'having a -tool shankreeeivingslot :and `Imeans for detachably 'clamping zv a toollbitainssaid slot, an axiallydisposed-.boresextending ffrom'said slot towardthe` oppositefendfof said bar, a plurality ofinterengaging--partition1formiing devices 1 disposed in said -borev.dividing the vr'annular. cavities; each of said cavitiesbeing-:paritially lled=withmercury, Iand ascrewgplugldis- I:posed:wholly vinwardly lof said slot 'closing the open `send of Lsaid boreAand simultaneously .ipressing said 1 partition :forming devices againsteach other and against-the bottomof said-bore.

12. ;A'boringbar for useiwith boringmills, vertical'latheszandV similarmachine tools.; -saidibar :having means f for` detachablyff clamping atool, bit at one Vend thereof, tan axially disposed-,bore

extending fromthe tool bitA carrying endthere- Vof, '-a v,plug closingthe-,open endvof -said-lbore, .means in said boref dividing the.interior Y thereof into -a plurality of axially lalign-ed annularcavities; Veach of said cavities being .partially .iilled withmercury;said-dividing meanscomprising a primary element includinga centralfdis'c Vengag- -ing the wallsof said borewitha press.iit, ailist shankmember projecting 'from one side' thereof and .engaging the end of saidbore andasec'ond shank member projecting 'from the` opposite side ofsaid disc, and aV plurality of secondarfynie'mbers each having a discengagingthe "wallslof saidborewith apresst'anda shank portion extendingtoward the open end` ofsaidbore; each of said secondary elementsbeinnext preceding element by engagement of the disc portion thereof withthe end of the shank of the preceding element, and said plug servingboth to close said bore and to engage the end of the shank of theoutermost of said secondary elements with resultant formation of one ofsaid cavities.

3. A vibration dampening boring bar for use with machine tools; said barhaving a transverse tool bit holding slot at one end thereof and meansfor clamping a tool bit in said slot, an axially disposed bore extendingfrom the inner face of said slot toward the opposite end of said bar, ascrew threaded plug closing the end of said bore, means in said boredividing the interior thereof into a plurality of axially alignedannular cavities; each of said cavities being partially filled withmercury; said dividing means comprising a primary element including acentral disc engaging the walls of said bore with a press fit, a iirstshank member projecting from one side thereof and engaging the end ofsaid bore and a second shank member projecting from the opposite side ofsaid disc, and a plurality of secondary members each having a discengaging the walls of said bore with a press t and a shank portionextending toward the open end of said bore; each of said secondaryelements being spaced from the next preceding element by engagement ofthe disc portion thereof with the end of the shank of the precedingelement, and said plug serving both to close said bore and to engage theend of the shank of the outermost of said secondary elements withresultant formation of one of said cavities.

LOYD Y. POOLE.

References Cited in the le of this patent UNITED STATES PATENTS Number

